Annealing of the photoluminescence W-center in proton-irradiated silicon

We study radiation defects generated by 55 MeV protons in float-zone silicon using photoluminescence (PL) and deep-level transient spectroscopy (DLTS). The investigated material is weakly phosphorus-doped and contains varying amounts of interstitial oxygen ( < 2 x 10(14)... 1.7 x 10(17) cm(-3)). Special attention is paid to the as of yet unidentified luminescence W-center. Its isochronal annealing behavior (40-160 degrees C) is discussed in conjunction with the evolution of the cluster damage-related features in the DLTS spectrum. We find the annealing rate of the W-center to be independent of the oxygen content and thus exclude oxygen as a constituent of the center. There is no evident correlation between the main peaks in the DLTS spectrum and the W-center. However, a weak signal at E(c)-0.075 eV is found to be a good candidate for a DLTS signal of the center. Further studies are needed to relate the formation of the W-center to the interstitials and/or vacancies released from damage clusters during annealing, which might help in identifying the constituents of the complex defect. (C) 1999 Elsevier Science B.V. All rights reserved.